U.S. Pat. No. 5,513,668 discloses an apparatus for wet treatment of a plate-like article comprising a spin chuck for holding and rotating comprising means for holding the plate-like article at the plate-like article's edge and a gas supply means for directing gas towards the side of the plate-like article, which is facing the spin chuck, wherein the gas supply means comprises a gas nozzle rotating with the spin chuck, for providing a gas cushion between the plate-like article and the spin chuck. Such a chuck is commonly known as Bernoulli-Chuck because the plate-like article is pulled towards the chuck by vacuum generated due to the aerodynamic paradox called Bernoulli-Effect. Such Bernoulli-chucks may comprise radially movable pins, wherein the pins securely hold the plate-like article even if no pressurized gas is providing the Bernoulli-Effect.
Alternatively Bernoulli-chucks may comprise non-movable pins on which the plate-like article rests (preferably on the plate-like article's edge region, where the mechanical contact does not harm the plate-like article). In this case the plate-like article is drawn towards the pins and securely held by Bernoulli-Effect.
For specific application it is advantageous to also apply liquid to the side of the plate-like article, which faces the chuck. Spin chucks with a gas supply towards the side of the plate-like article, which faces the chuck, (so called Bernoulli chucks) do not have a liquid supply nozzle for particle free rinsing of the side of the plate-like article, which faces the chuck. Furthermore, known spin chucks, which are designed for liquid treatment of both sides of a plate-like article, have no gas feed means for providing a gas cushion to have the plate-like article's side, which faces the spin chuck, protected from being wetted by treatment liquid.